NASA astrobiology announcement November 2010

[Orion1]

Washington (CNN) -- Scientists have discovered a form of bacteria that can thrive on arsenic -- an element generally considered toxic -- dramatically expanding both traditional notions of how life is sustained and the range of where it might be found in the universe, NASA funded-researchers said Thursday.

The bacterium -- strain GFAJ-1 of the Halomonadaceae family of Gammaproteobacteria -- was scooped from sediment in California's Mono Lake, an area rife with high levels of naturally occurring arsenic, it said.

Scientists were able to grow the microbes from the lake with only small portions of phosphorous -- considered an essential nutrient in the biomolecules of naturally occurring bacteria.

The bacterium not only grew but also incorporated the arsenic molecules into its DNA (As-DNA), in place of phosphorus, she said.

According to my understand of molecular biology, an organism based upon As-DNA - if that is the proper scientific nomenclature for such a molecule, represents a new class of life that is relatively distinct from P-DNA. Similarly, a new class of life would also be represented by Si-DNA or Silicon based life where Silicon is replaced by Carbon, however such a class of life would have to respire Silicon Dioxide instead of Carbon Dioxide, and because Silicon Dioxide is not a gas, such a class of life is highly improbable.

With further genetic engineering of this bacterium away from P-DNA evolution, it may be possible for the organism to completely substitute Arsenic as As-DNA.

Applications for such a bacterium could involve removing Arsenic from contaminated soils and water.

Is the probability of class As-Si-DNA based life in the Universe non-zero?
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Reference:
http://www.cnn.com/2010/US/12/02/nasa.extraterrestrial.life/index.html?hpt=T2"

 

[DaveC426913]

According to my understand of molecular biology, an organism based upon As-DNA ... represents a new class of life that is relatively distinct from P-DNA.

Ivan Semaniuk made a good point in a sound bite.

He suggested it is not so much that this bacterium is making As-DNA, simply that As is getting substituted for P in the existing DNA.

Kind of like hemoglobin taking up CO instead of O, only more permanent (probably better examples of substitutions out there).

 

[Ygggdrasil]

According to my understand of molecular biology, an organism based upon As-DNA - if that is the proper scientific nomenclature for such a molecule, represents a new class of life that is relatively distinct from P-DNA. Similarly, a new class of life would also be represented by Si-DNA or Silicon based life where Silicon is replaced by Carbon, however such a class of life would have to respire Silicon Dioxide instead of Carbon Dioxide, and because Silicon Dioxide is not a gas, such a class of life is highly improbable.

With further genetic engineering of this bacterium away from P-DNA evolution, it may be possible for the organism to completely substitute Arsenic as As-DNA.

Applications for such a bacterium could involve removing Arsenic from contaminated soils and water.

Is the probability of class As-Si-DNA based life in the Universe non-zero?

Isaac Asimov, who has a PhD in biochemistry in addition to being a science fiction writer, discussed the conditions for alternative biochemistries in his essay "Not as we know it." Although he doesn't discuss arsenic-based life, he does discuss possible conditions for silicon-based life:

http://www.bigear.org/CSMO/HTML/CS09/cs09p05.htm

 

[Ygggdrasil]

Can we really jump the gun to silicon based life? I mean, if the evidence is empirical, then we have an organism using "mostly" arsenic instead of it's usual diet. I would like to point out that these organisms are not totally weaned off of P-DNA. They just supposedly use arsenic in its place. I'm just curious if we have enough evidence to jump from arsenice to silicon here.

Definitely not, especially because Si-life would not be expected to function at the temperatures and pressures present on Earth. Furthermore, it's still not clear whether the organism actually functions using As-DNA instead of P-DNA. The NASA study has implications only on the possibility of replacing phosphorus with arsenic, and does not provide any support for or against the existence of other such element substitutions.

 

[Redbelly98]

They funded the research under a branch of exobiology. Basically trying to answer the question: "what else should we look for that might indicate life?"

Okay, sounds reasonable.

 

[HeLiXe]

Arsenic-based life tastes like chicken, but I hear it's not good for you.

Arsenic based life is chicken non organic anyways

 

[HeLiXe]

Ivan Semaniuk made a good point in a sound bite.

He suggested it is not so much that this bacterium is making As-DNA, simply that As is getting substituted for P in the existing DNA.

Kind of like hemoglobin taking up CO instead of O, only more permanent (probably better examples of substitutions out there).

This is interesting.

 

[Orion1]

DNA substitutions...

Ivan Semaniuk made a good point in a sound bite.

He suggested it is not so much that this bacterium is making As-DNA, simply that As is getting substituted for P in the existing DNA.

If the bacterium strain GFAJ-1 of the Halomonadaceae family of Gammaproteobacteria is introduced into an environment that is Phosphorus poor and Arsenic rich and the As-DNA substitutions are the result of quantum chemistry, then if this strain is introduced into an environment that is Phosphorus poor and Nitrogen rich, then by quantum chemistry would the strain substitute Nitrogen for Phosphorus as N-DNA?

Similarly, if this strain is introduced into an environment that is Carbon poor and Boron rich, then by quantum chemistry would the strain substitute Boron for Carbon as B-DNA?

Definitely not, especially because Si-life would not be expected to function at the temperatures and pressures present on Earth. Furthermore, it's still not clear whether the organism actually functions using As-DNA instead of P-DNA.

There is the possibility that these substituted R-DNA strands are completely non-functional and inert molecules and completely incapable of transcription and replication.
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[cronxeh]

So this announcement turned out to be somewhat boring. To me it was more along the lines of adaptation over a paradigm shift. Its nice to know that chemicals are relative to life, only the dynamics of evolution are essential in the long term.

 

[Orion1]

R-dna...

To me it was more along the lines of adaptation over a paradigm shift. Its nice to know that chemicals are relative to life, only the dynamics of evolution are essential in the long term.

If there is a paradigm shift in terms of quantum chemistry then the minimum qualification for R-DNA would include period 1,2,3 elements:
R-DNA (H,(B,C),N,O,P,S)

Then the maximum paradigm shift would include period 2,3,4 elements:
R-DNA (Li,Si,P,S,As,Se)

Including no paradigm shift to a complete paradigm shift, exactly how many different R-DNA substitution combinations are there?
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